Flotation machine

ABSTRACT

A flotation machine comprising a flotation cell, an air suction pipe to introduce air into the flotation liquid in said cell, a rotary member for stirring said flotation liquid and a diffuser, wherein the bottom plate of said flotation cell is provided with at least one suction-guide blade extending radially from a portion of the bottom plate below said rotary member toward the inner wall of said flotation cell.

United States Patent Nagahama 1 1 Sept. 30, 1975 [54] FLOTATION MACHINE2,696,913 12/1954 Anderson 209/169 2,966,266 12/1960 Coke 209 168 [751Invent: Talsuya Nagahama Japan 3,070,229 12/1962 Benozzo 209 170 x 73Assignee: Mitsui Mining & Smelting C0., 11, 31307-697 3/ 1967 Fahlstrom9t 209/170 X Tokyo Japan 3,378,141 4/1968 Warman 209/170 x 3,437,2034/1969 Nakamura 209/169 22 Filed: Aug. 22, 1974 Appl. No.: 499,770

Related U.S. Application Data Continuation of Ser. No. 333,681, Feb. 20,1973, abandoned.

Foreign Application Priority Data Feb. 21, 1972 Japan 47-17838 U.S. Cl.210/219; 209/169; 210/221; 261/87 Int. Cl. 801D l/14 Field of Search209/l68l70; 210/219-221; 261/87, 93

References Cited UNITED STATES PATENTS 6/1930 Jones et al. 210/219 XPrimary E.\aminer lohn Adee Assistant E.\'aminerRobert H. SpitzerAttorney, Agent, or FirmWoodhams, Blanchard and Flynn [5 7] ABSTRACT Aflotation machine comprising a flotation cell, an air suction pipe tointroduce air into the flotation liquid in said cell, a rotary memberfor stirring said flotation liquid and a diffuserQwherein the bottomplate of said flotation cell is provided with at least one suctionguideblade extending radially from a portion of the bottom plate below saidrotary member toward the inner wall of said flotation cell.

6 Claims, 2 Drawing Figures US. Patent Sept. 30,1975 3,909,413

HF 1 [wife W11 FLOTATION MACHINE This is a continuation of applicationSer. No. 333,681, filed Feb. 20, 1973, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a flotation machine which is capable of drawingmuch more air than the conventional flotation machines when operated onthe basis of a fixed value of power.

2. Description of the Prior Art A flotation machine is required toperform the function of generating bubbles within a flotation liquidconsisting of a liquid or pulp (a mixture of solid matters and water)introduced into it and floating said bubbles while making an ingredientof the flotation liquid attach to the bubbles to thereby separate saidingredient. Therefore, there is a need for a flotation machine capableof generating a great deal of bubbles. As a matter of fact, enhancementof the flotation efficiency can be achieved in proportion to the amountof the generated bubbles to some degree.

In the prior art, adjustment of the bubbles to be generated has beenachieved to some degree by the selection of the kind and amount of thefloating agent. However, inasmuch as the volume or amount of bubbles tobe generated generally depends on the volume of air to be introduced,such methods as increasing the introduction of air by intensifying thestirring of the flotation liquid or increasing the speed of rotation ofthe rotary member for stirring the flotation liquid, such as theimpeller or rotor, or positively blowing a lot of air into the flotationcell have hitherto been popular. But the former method has beendefective in that, when the introduction of air is increased byincreasing the speed of rotation of the rotary member of the flotationmachine, there is brought aboutnot only an increase in power comsumptionsuch as electric power, but also an increase in the degree of abrasionof the rotary member as well as the part holding the support meanstherefor. While; the latter method of positively blowing air into theflotation cell has been defective in that the preparation and supply ofpressurized air necessitates extra equipment and additional power.

BRIEF DESCRIPTION OF THE DRAWINGS In the appended drawings,

FIG. 1 is a vertical sectional view of the flotation-cell portion of aflotation machine which may be utilized in practicing one embodiment ofthe present invention, and

FIG. 2 is a cross-sectional view taken along the line II II in FIG. 1.In these drawings, 1 denotes the flotation cell, 2 denotes the impeller,3 denotes the shaft, 4 denotes the stand pipe (air suction pipe), 5denotes the fixed diffuser, 6 denotes the blades of said fixed diffuser,7 denotes the bottom plate of the flotation cell, 8 to 8" denoterespectively the suction-guide blade, and 9 denotes thefroth-discharging trough.

DETAILED DESCRIPTION OF THE INVENTION The present invention is intendedto provide an improved flotation machine which is capable ofautomatically drawing a great quantity of air therein without resortingto any special method of increasing the introduction of air such asdiscussed in the foregoing.

The inventorof the present invention has conducted a series ofresearches on how to increase the introduction of air in a flotationmachine having the construction that the air suction pipe such as thestand pipe or hollow shaft is held in a position parallel to the axis ofthe flotation cell and the bottom portion of the flotation cell isprovided with a rotary member for stirring the flotation liquid coupledwith a diffuser, and as a result, he has come to the finding that, whenthe speed of current of the flotation liquid forced out of the center ofthe flotation cell toward the inner wall thereof by the rotary member isincreased, the introduction of air through the air suction pipeincreases, and especially when the bottom plate of the flotation cell isprovided with a plate to control the direction of flow of the flotationliquid, the introduction of air increases remarkably.

The present invention is based on this finding obtained in the processof the foregoing researches.

Further particulars of the present invention will be discussed in thefollowing by reference to the appended drawings.

Except for the provision of the suction-guide blades 8 to 8", theconstruction of the flotation machine shown in these drawings is almostthe same as the well known conventional flotation machines.

In the drawings, when the flotation liquid is fed to the flotation cell1 and the impeller 2 is turned by the rotation of the shaft 3 in thedirection of the arrow, air is drawn in the stand pipe 4. Thisintroduction of air is carried out by virtue of the reduced pressureinside the fixed diffuser 5 when the flotation liquid is made to flowtoward the side wall of the flotation cell, passes the gaps between theplural blades 6 of said diffuser 5 and is diffused. When thesuction-guide blades 8 to 8 are provided on the bottom plate of theflotation cell as shown in the drawings, there is brought about theeffect that the introduction of air into the stand pipe 4 is remarkablyincreased. This effect is considered attributable to the fact that thevolume of the flotation liquid to be drawn in at the time of rotation ofthe impeller 2 increases and the volume of the flotation liquid to bediffused from the diffuser 5 per unit time increases accordingly. Inother words, it is considered that, as the speed of diffusion or thespeed of flow of the flotation liquid to be diffused through the gaps ofthe blades 6 of the diffuser 5 is increased, the degree of reduction inpressure inside the diffuser 5 remarkably increases as compared with thecase of dispensing with the suction-guide blades 8 to 8", and as aresult, the introduction of air also increases. According to the presentinvention, therefore, it is possible to introduce sufficiently a greatquantity of air into the flotation machine without increasing the speedof rotation of the impeller 2 while limiting to a small amount therequirement for increased power. Therefore, the volume of valuablesubstances to be transferred per unit time to the froth being dischargedfrom the froth-discharging trough 9 can be increased, contributing tothe rise of flotation efficiency.

Though the foregoing effect of the present invention can be obtainedeven when a single suction-guide blade is provided on the bottom plateof the flotation cell, the optimum number of said blades for use in thepresent invention is 4 or thereabouts. The shape of the suctionguideblade is desirable to be curved as indicated in the drawings, but it maybe of a straight rectangular form.

As to the place of installing the suction-guide blade on the bottomplate of the flotation cell, it is desirable to fix it so that the edgeof said blade is located directly below the rotary member such asimpeller or rotor, but is also will sufflce to dispose said edge ofblade at such a position on the bottom plate that it is spaced or lessfrom the circumference of rotation of the rotary member. Further, thesuction-guide blade can be installed in not only a round flotation cellbut also flotation cells of other shapes, and in all cases, it bringsabout the same effect.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1 There was employed aflotation machine (a) according to the present invention having aflotation cell of the same construction as shown in the appended drawingand equipped with a motor, another flotation machine (b) according tothe present invention in which the flotation machine (a) is modified byreplacing the curved suction-guide blades with straight rectangularblades which are disposed crosswise relative to the bottom plate andwhose edges are disposed directly below the circumference of rotation ofthe impeller 2 and a comparative flotation machine (c) having the sameconstruction as shown in the appended drawing except that thesuction-guide blades are omitted for the purpose of comparingefficiencies. Each flotation cell was charged with the same quantity ofwater and the speed of rotation of each impeller was identical. Thevolume of air drawn in through the stand pipe was measured respectively.The results were as shown in Table 1 below:

Table 1 Introducing quantity Flotation machine. of air (l/min./m

(flotation machine under present invention) (flotation machine underpresent invention) (comparative flotation machine) EXAMPLE 2 Table 2Distribution ratio of Cu Cu concentration in tailing after flotation(ppm) Flotation machine tailing froth (a) (flotation machine Table2-Continued Distribution ratio of Cu (7r) Cu concentration in tailingafter flotation (ppm) Flotation machine tailing froth under present 0.4L3 98.7 invention (h) (comparative 2.4 8.0 910 flotation machine)EXAMPLE 3 A zinc ore having the grade of 4.5% Zn was crushed into grainscomprising 18% of grains having the grain size of 65 mesh, and then apulp having 40% concentration of said grains was prepared. By addingcopper sulfate, sodium ethyl xanthate and a frother to this pulp,flotation was effected for 10 minutes respectively by means of the sameflotation machines as in Example cell having a continuous peripheralside wall and a bottom wall defining a flotation zone for containing aflotation liquid; a centrifugal pump impeller centrally located in saidcell, said impeller being rotatable about a vertical axis and beingdisposed close to but spaced upwardly from the bottom wall of the cell,said impeller comprising a plurality of circumferentially spacedelongated impeller blades extending parallel to said bottom wall formoving the flotation liquid adjacent thereto substantially horizontallyand radially outwardly toward said side wall; a stationary diffusingunit encircling said impeller and being disposed at the same verticallevel in said cell as said impeller, said diffusing unit comprising anannularly arranged series of substantially uniformly circumferentiallyspaced-apart, outwardly extending guide vanes arranged in a circulararray and located in the flow path of the liquid from the impeller forguiding and directing the flow of the liquid from the impeller outwardlyfrom said diffusing unit toward said side wall at a vertical levellocated close to but spaced upwardly from said bottom wall, the inneredges of said guide vanes defining a cavity within which said impelleris disposed for rotation therein, said diffusing unit having a centralopening in its bottom providing a liquid flow passage extending betweensaid cavity and a zone located adjacent said bottom wall and disposeddirectly below said impeller and said diffusing unit; an air inlet pipefor introducing air into the flotation liquid being pumped by saidimpeller, said air inlet pipe communicating with said cavity through theupper end thereof so that air is drawn into said cavity in response torotation of said impeller; and a plurality of circumferentiallyspaced-apart continuous stationary suction guide blades mounted on andprojecting upwardly from said bottom wall, said suction guide bladesextending inwardly from circumferentially spacedapart locations adjacentto said side wall along said bottom wall toward the center of said celland into said zone to a position directly underneath said impeller andsaid central opening of said diffusing unit, said suction guide bladesdefining therebetwecn horizontal open flow paths for flotation liquid,said open flow paths being open along their tops and closed along theirbottoms and sides, said flow paths being of progressively narrower widthin a direction from said side wall toward the center of said cell fordirecting return flow of flotation liquid to said cavity to increase thevolumetric rate of return flow of flotation liquid into said cavity inresponse to rotation of said impeller and thereby to increase the rateof air flow into said cavity, the upper edges of said guide blades insaid zone being located directly below and closely spaced from the loweredges of said impeller and said guide vanes, so that rotation of saidimpeller will draw air into said cavity and will mix the air with theflotation liquid and will forward the mixture of air and flotationliquid through said diffusing unit toward said side wall, and flotationliquid will return to said impeller along said bottom wall of said cellguided by said suction guide blades for repeated flow through saiddiffusing unit.

2. A flotation machine according to claim 1, in which said stationarydiffusing unit comprises a top plate affixed to the lower end of saidair inlet pipe and said guide vanes extend vertically downwardly fromsaid top plate around the periphery thereof and are arranged thereon ina circular array, the outer edges of said guide vanes beingsubstantially perpendicular to said bottom wall; said suction guideblades being uniformly spaced-apart and having continuous upperedges-disposed entirely bel'ow said impeller and said diffusing unit.

3. A flotation machine according to claim 2, in which said guide vanesare forwardly curved with respect to the direction of rotation of saidimpeller and said suction guide blades are rearwardly curved withrespect to the direction of rotation of said impeller.

4. A flotation machine according to claim 1, wherein said bottom wall isprovided with four suction-guide blades.

5. A flotation machine according to claim 1, wherein said suction-guideblades are so curved as to be convex in the direction of rotation ofsaid impeller.

6. A flotation machine according to claim 1, wherein said suction-guideblades consist of straight rectangular plates and disposed on saidbottom wall in cruciform arrangement.

1. A FROTH FLOTATION MACHINE, COMPRISING: A FLOTATION CELL HAVING ACONTINUOUS PERIPHERAL SIDE WALL AND A BOTTOM WALL DEFINING A FLOTATIONZONE FOR CONTAINING A FLOTATION LIQUID, A CENTRIFUGAL PUMP IMPELLERCENTRALLY LOCATED IN SAID CELL, SAID IMPELLER BEING ROTATABLE ABOUT AVERTICAL AXIS AND BEING DISPOSED CLOSE TO BUT SPACED UPWARDLY FROM THEBOTTOM WALL OF THE CELL, SAID IMPELLER COMPRISING A PLURALITY OFCIRCUMFERENTIALLY SPACED ELONGTED IMPELLER BLADES EXTENDING PARALLEL TOSAID BOTTOM WALL FOR MOVING THE FLOTATION LIQUID ADJACENT THERETOSUBSTANTIALLY HORIZONTALLY AND RADIALLY OUTWARDLY TOWARD SAID SIDE WALL,A STATIONARY DIFFUSING UNIT ENCIRCLING SAID IMPELLER AND BEING DISPOSEDAT THHE SAME VERTICAL LEVEL IN SAID CELL AS SAID IMPELLER, SAAIDDIFFUSING UNIT COMPRISING AN ANNULARLY ARRANGED SERIES OF SUBSTANTIALLYUNIFORMLY CIRCUMFERENTIALLY SPACED-APART, OUTWARDLY EXTENDING GUID VANESARRANGED IN A CIRCULAR ARRAY AND LOCATED IN THE FLOW PATH OF THE LIQUIDFROM THE IMPELLER FOR GUIDING AND DIRECTING THHE FLOW OF THE LIQUID FROMTHE IMPELLER OUTWARDLY FROM SAID DIFFUSING UNIT TOWARD SAID SIDE WALL ATA VERTICAL LEVEL LOCATED CLOSE TO BUT SPACED UPWARDLY FROM SAID BOTTOMWALL, THE INNER EDGES OF SAID GUIDE VANES DEFINING A CAVITY WITHIN WHICHSAID IMPELLER IS DISPOSED FOR ROTATION THEREIN, SAID DIFFUSING UNITHAVING A CENTRAL OPENING IN ITS BOTTOM PROVIDING A LIQUID FLOW PASSAGEEXTENDING BETWEEN SAID CAVITY AND A ZONE LOCATED ADJACENT SAID BOTTOMWALL AND DISPOSED DIRECTLY BELOW SAID IMPELLER AND SAID DIFFUSING UNIT,AN AIR INLET PIPE FOR INTRODUCING AIR INTO THE FLOTATION LIQUID BEINGPUMPED BY SAID IMPELLER, SAID AIR INLET PIPE COMMUNICATING WITH SAIDCAVITY THHROUGHH THE UPPER END THEREOF SO THAT AIR IS DRAWN INTO SAAICAVITY IN RESPONSE TO ROTATION OF SAID IMPELLER, AND A PLURALITY OFCIRCUMFERENTIALLY SPACED-APART CONTINUOUS STATIONARY SUCTION GUIDEBLADES MOUNTED ON AND PROJECTING UPWARDLY FROM SAID BOTTOM WALL, SAIDSUCTION GUIDE BLADES EXTENDING INWARDLY FROM CIRCUMFERENTIALLY SPACEAPART LOCATIONS ADJACENT TO SAID SIDE WALL ALONG SAID BOTTOM WALL TOWARDTHE CENTER OF SAID CELL AND INTO SAID ZONE TO A POSITION DIRECTLYUNDERNEATHH SAAID IMPELLER AND SAID CENTRAL OPENING OF SAID DIFFUSINGUNIT, SAID SUCTION GUIDE BLADES DEFINING THEREBETWEEN HORIZONTAL OPENFLOW PATHS FOR FLOTATION LIQUID, SAID OPEN FLOW PATHS BEING OPEN ALONGTHEIR TOPS AND CLOSED ALONG THEIR BOTTOMS AND SIDES, SID FLOW PATHSBEING OF PROGRESSIVELY NARROWER WIDTH IN A DIRECTION FROM SAID SIDE WALLTOWARD THE CENTER OF SAID CELL FOR DIRECTING RETURN FLOW OF FLOTATIONLIQUID TO SAID CAVITY TO INCREASE THE VOLUMETRIC RATE OR RETURN FLOW OFFLOTATION LIQUID INTO SAAID CABVITY IN RESPONSE TO ROTATION OF SAAIDIMPELLER AND THEREBY TO INCREASE THE RATE OF AIR FLOW INTO SAID CAVITY,THE UPPER EDGES OF SAID GUID BLADES IN SAID ZONE BEING LOCATED DIRECTLYBELOW AND CLOSELY SPACED FROM THE LOWER EDGES OF SAID IMPELLER AND SAIDGUIDE VANES, SO THAT ROTATION OF SAID IMPELLER WILL DRAW AIR AINTO SAIDCAVITY AN WILL MIX THE AIR WITH THE FLOTATION LIQUID AND WILL FORWARDTHE MIXTURE OF AIR AND FLOTATION LIQUID THROUGH SAID DIFFUSING UNITTOWARD SAID SIDE WALL, AND FLOTATION LIQUID WILL RETURN TO SAID IMPELLERALONG SAID BOTTOM WALL OF SAID CELL GUIDED BY SAID SUCTION GUIDE BLADESFOR RREPEATED FLOW THROUGH SAID DIFFUSING UNIT.
 2. A flotation machineaccording to claim 1, in which said stationary diffusing unit comprisesa top plate affixed to the lower end of said air inlet pipe and saidguide vanes extend vertically downwardly from said top plate around theperiphery thereof and are arranged thereon in a circular array, theouter edges of said guide vanes being substantially perpendicular tosaid bottom wall; said suction guide blades being uniformly spaced-apartand having continuous upper edges disposed entirely below said impellerand said diffusing unit.
 3. A flotation machine according to claim 2, inwhich said guide vanes are forwardly curved with respect to thedirection of rotation of said impeller and said suction guide blades arerearwardly curved with respect to the direction of rotation of saidimpeller.
 4. A flotation machine according to claim 1, wherein saidbottom wall is provided with four suction-guide blades.
 5. A flotationmachine according to claim 1, wherein said suction-guide blades are socurved as to be convex in the direction of rotation of said impeller. 6.A flotation machine according to claim 1, wherein said suction-guideblades consist of straight rectangular plates and disposed on saidbottom wall in cruciform arrangement.